During recent years, when an electroluminescent device is formed in a display device, electroluminescent materials of different colors need to be coated, and coating the electroluminescent materials by an ink-jet method is the most efficient and the pattern so formed is the most accurate.
When the ink-jet method is adopted to coat the electroluminescent material, in order to define a coating region and prevent the electroluminescent material solution from flowing into adjacent pixels, a bank structure needs to be formed on the display device. FIG. 1 is a schematic diagram of the cross section of the electroluminescent material solution formed in the bank structure through the ink-jet method in the prior art; and FIG. 2 is a structural schematic view of the bank structure and a first electrode. As illustrated in FIGS. 1 and 2, the bank structure 4 is formed on a base substrate 1 and a thin film transistor 2, the bank structure 4 defines an ink-jet region 16, and a first electrode 3 is formed in the ink-jet region 16. In the prior art, the ink-jet method is adopted to drip an electroluminescent material solution 5 on the first electrode 3, the electroluminescent material solution 5 gathers within the ink-jet region 16, and then, a drier is used to dry the electroluminescent material solution 5 within the ink-jet region 16, thus an electroluminescent layer is formed on the first electrode 3.
FIG. 3a is a schematic diagram of the cross section of the electroluminescent layer formed through drying treatment when the inner side of the bank structure is lyophilic, and FIG. 3b is a schematic diagram of the cross section of the electroluminescent layer formed through drying treatment when the inner side of the bank structure is lyophobic. As illustrated in FIGS. 3a and 3b, during drying treatment, if the inner side of the bank structure 4 is lyophilic, a portion of the electroluminescent material solution 5 is adhered to the inner wall of the bank structure 4, so that the peripheral region of the finally formed electroluminescent layer 6 has a relative large thickness, while the thickness of the middle region is relative small, i.e., the electroluminescent layer 6 presents a “depressed” shape. If the inner side of the bank structure 4 is lyophobic, the electroluminescent material solution 5 will gather at the middle portion so that the peripheral region of the finally formed electroluminescent layer 6 has a relative small thickness while the middle region has a relative large thickness, i.e., the electroluminescent layer 6 presents a “protrusion” shape. Thus, the film thickness of the finally formed electroluminescent layer is uneven no matter the inner side of the bank structure is lyophilic or lyophobic, while the electroluminescent layer with the uneven thickness easily causes color loss or color unevenness when emitting light, thus the performance of the electroluminescent device is affected.